A prime objective sought by the development of new delivery or release systems for active ingredients is the controlled delivery of an active agent, especially a pharmacological agent, to a site of action at an optimum rate and therapeutic dose. Improvements in therapeutic index may be obtained by modulating the distribution of the active ingredient in the body. Association of the active ingredient with a delivery system enables, in particular, its specific delivery to the site of action or its controlled release after targeting the action site. By reducing the amount of active ingredient in the compartments in which its presence is not desired, it is possible to increase the efficacy of the active ingredient, to reduce its toxic side effects and even modify or restore its activity.
Colloidal delivery systems for active ingredients include liposomes, microemulsions, nanocapsules, nanospheres, microparticles and nanoparticles. Nanoparticles offer the advantages of targeting, modulation of distribution and flexible formulation and have a polymer structure which may be designed and produced in a manner that is adapted to the desired objective. They have proved to be particularly promising for obtaining an improved therapeutic index as defined above due to their ability to ensure controlled release, specific delivery to the action site or targeted delivery allowing both an increase in efficacy and a reduction in toxic side effects on other organs.
This type of administration uses biodegradable polymers. Among these, poly(alkyl) cyanoacrylates) are of special interest since their bioerosion occurs rapidly in comparison with other biodegradable polymers and takes place during periods of time that are compatible with therapeutic or diagnostic applications.
Despite these characteristics of interest, the active ingredient content capacity of nanoparticles of poly(alkylcyanoacrylates), expressed in quantity of active ingredient associated with a mass unit of polymer, is often limited, especially when the active ingredient is only scarcely soluble in water since the production of nanoparticles uses polymerization techniques in an aqueous medium. This considerable limitation of the active ingredient content capacity is especially observed with hydrophobic, amphiphlic and/or insoluble active ingredients.
The relatively low ability of conventional nanoparticles to carry an adequate quantity of active ingredients from the administration site to the target site in the body often risks leading to the necessary administration of considerable quantities of polymers.
Poly(alkylcyanoacrylates) are used to produce nanoparticles as vectors of active ingredients. However, for the above-mentioned reasons, the low vectors loads obtained, especially with hydrophobic, amphiphilic and/or water insoluble active ingredients, restrict their therapeutic use.